CHEM10050 : Guiry Lecture 14 - Aldehydes, Acetals and Polysaccharides

What is the product formed when an alcohol adds to the carbonyl group of an aldehyde?

a) Hemiketal

b) Hemiacetal

c) Acetal

d) Ketal

b) Hemiacetal

In the formation of a hemiacetal, which atom attacks the carbonyl group of the aldehyde?

a) Hydrogen

b) Carbon

c) Oxygen

d) Nitrogen

c) Oxygen

What is the difference between a hemiacetal and an acetal?

a) Hemiacetals are unstable, while acetals are stable

b) Hemiacetals are formed by the reaction of an alcohol with a ketone, while acetals are formed by the reaction of an alcohol with a hemiacetal

c) Acetals have two ether groups, while hemiacetals have only one

d) Acetals can be isolated, while hemiacetals cannot

d) Acetals can be isolated, while hemiacetals cannot

What is the equilibrium relationship between the open-chain form and the ring-closed forms of glucose?

a) α-glucose → β-glucose → open-chain form

b) β-glucose → α-glucose → open-chain form

c) open-chain form → α-glucose → β-glucose

d) open-chain form → β-glucose → α-glucose

b) β-glucose → α-glucose → open-chain form

What is the percentage of β-D-glucose at equilibrium when it is in equilibrium with the open-chain form?

a) 36%

b) 64%

c) Less than 0.02%

d) 100%

b) 64%

Why does the Benedict's test work for glucose?

a) Because glucose is an aldehyde

b) Because glucose is a ketone

c) Because glucose can form a hemiacetal

d) Because glucose can form an acetal

c) Because glucose can form a hemiacetal

What is the key difference between a hemiketal and a hemiacetal?

a) A hemiketal is formed from a ketone, while a hemiacetal is formed from an aldehyde

b) A hemiketal is formed from an aldehyde, while a hemiacetal is formed from a ketone

c) A hemiketal has one ether group, while a hemiacetal has two

d) A hemiketal is unstable, while a hemiacetal is stable

a) A hemiketal is formed from a ketone, while a hemiacetal is formed from an aldehyde

What is the product formed when an alcohol reacts further with a hemiacetal?

a) Hemiketal

b) Hemiacetal

c) Acetal

d) Ketal

c) Acetal

What is the catalyst or enzyme needed for the formation of an acetal from a hemiacetal?

a) Acid catalyst

b) Base catalyst

c) H+ catalyst or enzyme

d) OH- catalyst or enzyme

c) H+ catalyst or enzyme

What is the difference between a hemiacetal and a ketal?

a) Hemiacetals are formed from aldehydes, while ketals are formed from ketones

b) Hemiacetals have one ether group, while ketals have two

c) Hemiacetals are unstable, while ketals are stable

d) Hemiacetals react with alcohols, while ketals do not react with alcohols

a) Hemiacetals are formed from aldehydes, while ketals are formed from ketones.

What type of bond holds many sugars and complex carbohydrates together?

a) Ester bond

b) Acetal bond

c) Amide bond

d) Peptide bond

b) Acetal bond

What is the product of the hydrolysis of an acetal?

a) Alcohol and a ketone

b) Alcohol and an aldehyde

c) Alcohol and a hemiacetal

d) Ketone and a hemiacetal

c) Alcohol and a hemiacetal

Which disaccharide is linked via a β(1-4) linkage to glucose?

a) Maltose

b) Sucrose

c) Lactose

d) Fructose

c) Lactose

What type of reaction is hydrolysis of an acetal?

a) Addition

b) Substitution

c) Elimination

d) Isomerization

b) Substitution

Which of the following is a product of the hydrolysis of maltose?

a) Glucose and fructose

b) Glucose and galactose

c) Glucose and maltose

d) Glucose and glucose

d) Glucose and glucose

What is the difference between a hemiacetal and an acetal?

a) Hemiacetals are formed from aldehydes, while acetals are formed from ketones.

b) Hemiacetals have one ether group, while acetals have two.

c) Hemiacetals are intermediates in the formation of acetals.

d) Hemiacetals are stable enough to be isolated, while acetals are not.

d) Hemiacetals are stable enough to be isolated, while acetals are not.

What is the only chemical reaction of acetals?

a) Reduction

b) Oxidation

c) Hydrolysis

d) Esterification

c) Hydrolysis

Which of the following is not a product of the hydrolysis of lactose?

a) β-galactose

b) α-galactose

c) β-glucose

d) α-glucose

b) α-galactose

Which linkage is present in maltose?

a) α(1-2) linkage

b) β(1-2) linkage

c) α(1-4) linkage

d) β(1-4) linkage

d) β(1-4) linkage

How are many sugars and complex carbohydrates held together?

a) Ester bonds

b) Acetal bonds

c) Amide bonds

d) Peptide bonds

b) Acetal bonds

Which of the following is a polysaccharide?

a) Glucose

b) Maltose

c) Starch

d) Sucrose

c) Starch

What are the two types of polymers in starch?

a) Amylose and cellulose

b) Amylose and amylopectin

c) Amylopectin and glycogen

d) Glycogen and cellulose

b) Amylose and amylopectin

What is the storage form of glucose in animals?

a) Starch

b) Glycogen

c) Cellulose

d) Fructose

b) Glycogen

How are glucose units joined in starch?

a) β(1-4) linkage

b) α(1-4) linkage

c) α(1-2) linkage

d) β(1-2) linkage

b) α(1-4) linkage

Which of the following has an amylopectin-like polymer?

a) Starch

b) Glycogen

c) Cellulose

d) Maltose

a) Starch

What is the function of cellulose's structure?

a) To store glucose

b) To increase fibre strength

c) To provide energy

d) To transport glucose

b) To increase fibre strength

What is the difference between α and β glucose?

a) The position of the -OH group on the anomeric carbon

b) The position of the -OH group on carbon 6

c) The number of carbon atoms in the molecule

d) The type of bond between glucose units

a) The position of the -OH group on the anomeric carbon

What is the bond that cellulose contains that humans cannot break down?

a) α(1-4) bond

b) β(1-4) bond

c) α(1-6) bond

d) β(1-6) bond

b) β(1-4) bond

Where is glycogen stored in the body?

a) In the liver and muscle tissue

b) In the pancreas

c) In the brain

d) In the bloodstream

a) In the liver and muscle tissue

What organisms have enzymes to hydrolyze β(1-4) bonds?

a) Humans

b) Cattle

c) Both humans and cattle

d) No organisms can hydrolyze β(1-4) bonds

b) Cattle